Biology subjects

Polster, B. M.

Publications and source records attributed to Polster, B. M..

4 recordsLinked to original sources

bioRxiv2026

HAPI Cells are SIM-A9-related Mouse Microglial Cells Useful for In Vitro Modeling of Microglial Immunometabolism

Highly aggressively proliferating immortalized (HAPI) cells were initially described as a spontaneously immortalized rat cell line isolated from a mixed neonatal rat glial population. It was demonstrated that HAPI cells are phagocytic, stain for macrophage-/microglia-specific markers like CD11b and GLUT5, and exhibit lipopolysaccharide (LPS)-induced nitric oxide (NO) and tumor necrosis factor-alpha (TNF-) release. These characteristics led to their widespread use as a rat microglial cell line. Here, we report that HAPI cells are mouse cells, not rat cells, but further establish that they have a microglia-like identity and properties useful for in vitro modeling. Cell line authentication by short tandem repeat (STR) profiling, a method that detects identifying DNA signatures, indicates that HAPI cells are a 100% match for SIM-A9 cells, a mouse microglial cell line reported to be spontaneously immortalized from primary cell culture. We find that both HAPI cells and SIM-A9 cells express the microglia-selective gene Tmem119, as well as the microglia-/macrophage-selective marker Cx3cr1, supporting a microglial origin. Like primary rodent microglia or macrophages, HAPI cells respond to combined stimulation with LPS and the Type II interferon, interferon-gamma (IFN-{gamma}), with a pro-inflammatory morphology, NO production, NO-dependent suppression of mitochondrial oxygen consumption, and increased extracellular acidification (an indicator of glycolysis). The Type I interferon, interferon-alpha (IFN-), also reduces mitochondrial oxygen consumption when administered alone or in combination with LPS. Overall, results indicate that HAPI cells are SIM-A9-related mouse cells of microglial origin and support their continued use to study microglial behavior in vitro, including immunometabolism.

neuroscience↗

bioRxiv2025

CRABS-ROC, A Respirometry Protocol For Overcoming Substrate Limitations, Reveals Excess Brain Mitochondrial Complex I Capacity

Mitochondrial bioenergetic competency in cells is frequently assessed by the Mito Stress Test protocol, which includes uncoupler addition for evaluating respiratory capacity. The uncoupled oxygen consumption rate (OCR) is usually defined as maximal respiration, with little consideration of whether the measured rate is restricted by substrate supply. In this study, we show that the uncoupled OCR is substrate-limited in rat primary cortical neurons and isolated mouse forebrain synaptosomes. We use a different respirometry protocol we name CRABS-ROC (Complex Respirometry Assay Bypassing Substrate-Restricted Oxygen Consumption) that enables evaluation of individual electron transport chain (ETC) complex capacity using saturating levels of substrate to bypass this restriction. Applying CRABS-ROC to primary cortical neurons reveals >2-fold excess Complex I capacity beyond the uncoupled OCR of cells metabolizing glucose and pyruvate. Furthermore, we demonstrate that CRABS-ROC can expose a Complex I deficit in isolated harlequin mutant brain mitochondria that display wild-type levels of Complex I-substrate-linked respiration despite having about half the normal level of Complex I. Thus, CRABS-ROC should be broadly useful for studies on mitochondrial function because it can both reveal excess ETC capacity and unmask ETC alterations that may be missed by the most widely used methods.

cell biology↗

bioRxiv2025

Idebenone Enhances the Early Microglial Response to Traumatic Brain Injury and Mitigates Acute Gene Expression Changes to Ephrin-A and Dopamine Signaling Pathways

Traumatic Brain Injury (TBI) leads to persistent pro-inflammatory microglial activation implicated in neurodegeneration. Idebenone, a coenzyme Q10 analogue that interacts with both mitochondria and the tyrosine kinase adaptor SHC1, inhibits aspects of microglial activation in vitro. We used the NanoString Neuropathology panel to test the hypothesis that idebenone post-treatment mitigates TBI pathology-associated acute gene expression changes by moderating the pro-inflammatory microglial response to injury. Controlled cortical impact to adult male mice increased the microglial activation signature in peri-lesional cortex at 24 hours post-TBI. Unexpectedly, several microglial signature genes upregulated by TBI were further increased by post-injury idebenone administration. However, idebenone significantly attenuated TBI-mediated perturbations to gene expression associated with behavior, particularly in the gene ontology:biological process (GO:BP) pathways "ephrin receptor signaling" and "dopamine metabolic process." Gene co-expression analysis correlated levels of microglial complement component 1q (C1q) and the neurotrophin receptor gene Ntrk1 to large (>3-fold) TBI-induced decreases in dopamine receptor genes Drd1 and Drd2 that were mitigated by idebenone treatment. Bioinformatics analysis identified SUZ12 as a candidate transcriptional regulator of idebenone-modified gene expression changes. Overall, results suggest that idebenone enhances TBI-induced microglial proliferation within the first 24 hours of TBI and identify Ephrin-A and dopamine signaling as novel idebenone targets.

neuroscience↗

bioRxiv2023

Metabolic disruption impacts tick fitness and microbial relationships

Arthropod-borne microbes rely on the metabolic state of a host to cycle between evolutionarily distant species. For instance, arthropod tolerance to infection may be due to redistribution of metabolic resources, often leading to microbial transmission to mammals. Conversely, metabolic alterations aids in pathogen elimination in humans, who do not ordinarily harbor arthropod-borne microbes. To ascertain the effect of metabolism on interspecies relationships, we engineered a system to evaluate glycolysis and oxidative phosphorylation in the tick Ixodes scapularis. Using a metabolic flux assay, we determined that the rickettsial bacterium Anaplasma phagocytophilum and the Lyme disease spirochete Borrelia burgdorferi, which are transstadially transmitted in nature, induced glycolysis in ticks. On the other hand, the endosymbiont Rickettsia buchneri, which is transovarially maintained, had a minimal effect on I. scapularis bioenergetics. Importantly, the metabolite {beta}-aminoisobutyric acid (BAIBA) was elevated during A. phagocytophilum infection of tick cells following an unbiased metabolomics approach. Thus, we manipulated the expression of genes associated with the catabolism and anabolism of BAIBA in I. scapularis and detected impaired feeding on mammals, reduced bacterial acquisition, and decreased tick survival. Collectively, we reveal the importance of metabolism for tick-microbe relationships and unveil a valuable metabolite for I. scapularis fitness.

microbiology↗